/Engine/Plugins/FX/Niagara/Source/NiagaraEditor/Public/ViewModels/HierarchyEditor/NiagaraHierarchyViewModelBase.h
Prepares the items we want to create a hierarchy for. Primary purpose is to add children to the source root to gather the items to display in the source panel. The root view model is also given as a way to forcefully sync view models to access additional functionality, if needed
virtual void PrepareSourceItems ( [UNiagaraHierarchyRoot](API\Plugins\NiagaraEditor\ViewModels\HierarchyEditor\UNiagaraHierarchyRoot) * SourceRoot, [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [FNiagaraHierarchyRootViewModel](API\Plugins\NiagaraEditor\ViewModels\HierarchyEditor\FNiagaraHierarch-_9) > SourceRootViewModel )